2 options for running power under the dash
1. you can pass the power wire through the clutch gromit if its an auto then run the wire down the kick panel and up the right drivers side of the car.
2. pass it through where the existing loom enters the engine bay (difficult) then again run it down the drivers side.
once u've run it down the drivers side, remove the bottom part of the seat, then remove the drivers side back seat, back rest (upright bit) by undoing the 10mm bolt, and lift the back rest off. u'll see where the boot loom runs up the arch, then through a hole above the wheel arch, pass the wire through there. then u can place the back seat back together.
run ur speaker RCA's and wires down the passengers side of the car, there is a hole in the same spot on the other side behind the back rest.